James Pinsky: Getting the dirt on soil

James Pinsky


In the conservation world, dirt is a four letter word.

We prefer you say soil, which technically is still a four-letter word …

No, soil is a lot more to conservationists than the gritty stuff that led to the invention of washing machines; the waterless mud supports just about any and all life on Earth. So, it’s kind of a big deal.

Let’s learn more about our dirty little friend: soil is actually a three-dimensional natural body covering most of our planet’s land areas. It forms from weathering and erosion of bedrock, the formation of minerals in the soil as part of weathering, and the activities of plants and animals that influence soil characteristics.

Terrific. So aside from keeping bleach and washing machine makers in business, what else is dirt, err … soil good for?

Soil is incredibly important to us. Thanks to some information provided by the Tennessee Association of Resource Conservation and Development Councils we know soil serves as the mechanical support of plants and their root systems, serves as a reservoir for water and plant nutrients, and is an essential natural resource like air and water that are necessary for the existence of life on Earth.

We also know that whatever soil we have is all we will get because soil is not a renewable resource. Why? It’s because the process to make soil is slower than a line at the Department of Motor Vehicles on Monday morning. In fact, the soil formation processes take so long that we simply can’t fathom it in human terms. Whoa. So making soil takes longer than the commute on Interstate 66 West from Fairfax to Gainesville on a Friday at 5 p.m.? Not, quite, nothing is that long, but you get the point.

So, this soil thing that matters so much, what’s it made of? Our friends at the Tennessee Association of Resource Conservation and Development Councils tell us in their soils guide that it’s composed of five main components – mineral matter, organic matter, water, air, and living organisms. The Volunteer State conservationists break down the information even more by telling us that mineral matter is the major constituent of most soils, which comes from the weathering of rocks. The guide tells us the mineral portion of the soils is divided into three size constituents of particles less than 2 millimeters (mm) in diameter, sand, silt and clay.

This is useful information Jay. Thanks. But, I’m wondering. When is soil a rock and when is rock soil? Our good friends at the Tennessee Association of Resource Conservation and Development Councils have an answer: Any particle larger than 2 mm is not considered soil, but is called a rock

Other things not considered part of soil are organic matter or humus, and living roots and organisms.

Here are some more useful things to know about soil from the Tennessee Association of Resource Conservation and Development Councils:

Organic matter makes up between 0 and about 18 percent of most soils.

Organic matter tends to give soil a dark color. These soils are sometimes referred to as dark or “rich” soils.

Organic material is most often concentrated near the soil surface or topsoil because it is derived mostly from the breakdown of plant materials. The lower part of the soil or subsoil generally decreases in amount of organic matter with depth.

Soil organic matter can retain water in the soil for plant use and is chemically active to be able to store nutrients, pollutants, or other chemicals.

The presence of organic matter in the soil makes the topsoil easier to plow, till, and plants to grow in by improving soil structure, which adds more pore space, water, and air to allow other materials to move easier through the soil.

So, now you have the scoop on soil. To learn more about soil and even water, feel free to contact us here at Lord Fairfax Soil and Water Conservation District.

Special note: On Wednesday, local high schools will compete in our 2017 Envirothon at the Northern Virginia 4H Education Center in Front Royal.

James Pinsky is the Education and Information Coordinator for the Lord Fairfax Soil and Water Conservation District. Contact him at 540.465.2424, ext. 104, or james.pinsky@lfswcd.org. Visit us at www.lfswcd.org or follow us on Twitter https://twitter.com/lfswcd.